Saturated hydrocarbon compositions



Patented Nov. 3, 1953 UNITED STATE TENT OFFICE SATURATED HYDROCARBONCOMPOSITIONS No Drawing. Original application December 29,

1949, Serial No. 135,843. Divided and this application September 25,1950, Serial No. 186,688

2 Claims.

The present invention is directed to improved compositions suitable foruse as motor fuels. More particularly the invention is directed to motorfuel compositions comprising alkanes having branched structures.

This application is a division of U. S. Serial No. 135,843 filedDecember 29, 1949, in the names of Henry G. Schutze and Harry E. Cierand entitled Branched Chain Compositions and Method of Preparing Same,now abandoned.

It is the main object of the present invention to produce a mixture ofalkanes having branched structures which is suitable for use as anaviation or motor fuel.

Another object of the present invention is to provide a method forsynthesizing a product comprising saturated branched chain hydrocarbonsfrom a mixture of at least two saturated hydrocarbons.

A still further object of the present invention is to provide a processfor reacting a mixture of at least two saturated hydrocarbons to producea product having a molecular weight and structure diiierent from that ofthe saturated hydrocarbons in the mixture.

The present invention may be described briefly as involving the reactionof atle-ast two saturated hydrocarbons of different molecular structureby exposing the mixture to a resonance frequency radiation in thepresence of a metal sensitizing agent at a reaction temperature andpressure to form a product having a branched structure. The inventionparticularly contemplates reacting saturated paraflinic hydrocarbons ina mixture containing at least two saturated hydrocarbons of difierentmolecular weights and/or structure at a temperature in the range between80 and 650 F. and at least atmospheric pressure to form a product havinga molecular weight and structure different from that of the saturatedhydrocarbons in the mixture. The product in itself forms an improvedcomposition comprising a mixture of alkanes and particularly dimethyl,trimethyl and tetramethyl alkanes which is particularly suitable for usein motor fuels.

The invention is directed to employing at least two saturatedhydrocarbons of different molecular structure having from two to sixcarbon atoms in the molecule whereby a product is obtained whichcontains from six to twelve carbon atoms in the molecule and comprisingalkanes having from two to five methyl groups substituted for hydrogen.

In practicing the present invention the feed mixture is contacted in thepresence of a metal sensitizing agent with a resonance frequencyradiation sufiicient to activate the weakest carbonhydrogen bond in eachmolecule to cause the mixture of hydrocarbons to react and form aproduct having a diiferent molecular weight and structure from that ofthe saturated hydrocarbons in the mixture. After the reaction has beencompleted the products which are primarily saturated hydrocarbons havinga highly branched structure are separated from the metal sensitizingagent which is usually present in only small quantities, and theunconverted portion of the reaction product may, if desired, besubjected to contact with a metal sensitizing agent again and re-exposedto and energy content in the activated state.

' ergizing the metal sensitizer.

radiant energy to cause further reaction thereof.

The metal sensitizing agent employed in the present invention may be anymetal which meets the conditions set out below, including proper vaporpressure, light absorption characteristics,

Whatever metal sensitizer is employed it is incorporated in the reactionmixture of hydrocarbons, and the mixture is subjected to radiant energycontaining frequencies which are capable of en- In selecting a metalsensitizer and a source of radiant energy for the reaction, thefollowing conditions must be met:

(A) The vapor pressure of the metal employed as a sensitizer must besufiicient to insure that metal vapor is present in the hydrocarbonmixture in a concentration sufficient to absorb the.

activating light efliciently and to an extent that will permit rapidreaction to take place; conveniently, this vapor pressure is at least0.001

mm. of mercury at a temperature below about.

(B) The radiant energy must be of a frequency that can be absorbed bythe metallic sensitizer in its ground state in the hydrocarbon mixture.This frequency must correspond to at least one of the resonance lines ofthe metal sensitizer.

(C) The sum of the energy of the resonance frequency absorbed by themetal sensitizer and of the energy of the metal-hydrogen bond mustcorrespond to an energy content equal .to or in excess of that requiredto rupture one of the parafiin C-H bonds.

While a number of metal sensitizing agents will fill some of theforegoing requirements, the preferred metal sensitizing agents incarrying out our invention are the metals of subgroup B of group II ofthe periodic table, namely mercury, cadmium and zinc. While either ofthese metals Resonance Element lmes A The saturated hydrocarbons findinguse in the present invention include, as pairs, ethane and propane,propane and 'isobutane, propane and n-butane, propane and n-pentane,propane and isopentane, n-butane and isopentane, n-butane and isobutane,isobutane and isopentane, propane and 2,2-dimethyl butane, propane and2,3- dimethyl pentane, and many more pairs of saturated hydrocarbons toonumerous to mention here, but illustrated by the foregoing pairs ofreactants. In general, due to its relative inactivity, methane will notbe a desirable reactant. However, our invention may be employed inmethylation reactions, such, for example, as the reaction of methane andn-butane to produce isopentane.

The reaction may be conducted at a temperature in the range from about80 to 659 F. and pressures may be substantially atmospheric and rangingupwardly therefrom. A preferred temperature range is from 100- to 400 F.The temperature and pressure within the range given will be selected toprovide a vapor phase.

The process of the present invention is not limited to any particulartype of equipment. The reaction has been carried out satisfactorily inan annular reactor consisting of a cylindrical outer Pyrex jacketprovided with an inlet at one end and an outlet at the other end, theinner cylinder emanating light of the desired wave length. For example,when it is desired to employ mercury as the metallic sensitizer, amercury vapor lamp emanating light of 2537 A. wave length is inserted asa concentric inner cylinder in the Pyrex jacket. When employing mercuryas a sensitizer, the lamp should be operated in such a manner that anunreversed 2537 A. line i obtained. A satisfactory lamp for such apurpose is, for example, the General Electric 15 watt T-8 GermicidalLamp, or a lamp such as described in U. S. Patent 2,473,642 to Found etal.

When cadmium is used as the metallic sensitizer, a cadmium lamp may beemployed. The reactor jacket may be surrounded with a suitable heatingmeans such as an electric heater or a furnace. In converting the mixtureof parafiinic hydrocarbons to other branched chain hydrocarbons, theparaifinic hydrocarbon feed is vaporized and introduced into the jacketthrough the inlet, and the products of reaction are withdrawn throughthe outlet. In carrying out a mercurysensitized reaction a satisfactorymethod of maintaining mercury sensitizer in the reactor has been toplace a small amount of metallic mercury into the reactor jacket priorto the beginning of the reaction, Other satisfactory methods ofintroducing metal sensitizer are known; for example, a carrier stream.consisting of the vaporized hydrocarbon feed, or a portion thereof, oran inert gas, such as nitrogen, may be passed through a vesselcontaining the metal sensitizer in the liquid or vapor state prior topassing said carrier stream into the reactor.

In preparing the feed stock for carrying out the process according toour invention, the conventional methods of purification, such asabsorption or fractionation, may be employed. The two reactant parafiinhydrocarbons may be prepared in separate streams of high purity andcombined in the desired proportion prior to being fed into the reactor.High purity reactant streams are, however, not essential to the carryingout of our invention. Particularly, it is not disadvantageous for thefeed stream to contain compounds which are considerably less reactive atthe reaction conditions employed than the reactants whose prodnot isdesired. It is contemplated that the feed mixture will contain at leasttwo saturated hydrocarbons of difierent molecular structure. Themolecular Weight of the reacted hydrocarbons may be the same, but it isessential that the structure should be different. ferred that the feedmixture contain only the two reactant hydrocarbons, actually in practiceit may be desirable to have more than two hydrocarbons in the mixture.Thus the feed stock may contain, for example, propane and isobutane, asWell as n-butane and all three of the hydrocarbons would then enter intothe reaction. Attention should be paid to the exclusion of impuritieswhich may react with the feed or sensitizer to produce undee sirablecontaminatin compounds. For example, water vapor, in low concentration,may not be harmful to the mercury sensitizer, but it may oxidizecadmium. Reactive compounds other than the hydrocarbons desired to reactwill cause side reactions to take place which may form less desirableproducts. However, they may not cause the sensitizer to deteriorate.

The efliuent leaving the reactor in which a process according to ourinvention is carried out may contain unconverted feed hydrocarbons aswell as the branched chain product. The total eflluent may be subjectedto condensation to recover the feed and product in the liquid phase, andhydrogen and other non-condensibles in the gas phase. A part of thetotal liquid eflluent may be recycled to the reactor to increase theyield of branched chain product from the original feed, and a part orall of the total liquid effluent may be subjected to fractionaldistillation in order to recover the branched chain hydrocarbon productsin substantially pure form.

Actually, it may be desirable to recover the product as is and simplysubject it to distillation to recover the unreacted hydrocarbons whichmay be recycled as mentioned before. It may be desirable not to separatethe branched chain alkanes which are formed as a result of the improvedreaction because the compounds as produced form an extremely desirablemotor fuel. In fact, when the feed stock is propane and isobutane theproduct consists of 2,2,3-trimethylbutane, 2,2,3,3-tetramethylbutane and2,2,33,4- pentamethylpentane with a .minor amount of other materials. Itwill be seen that this mixture comprises triptane, a very desirablehydrocarbon, the solid octane, 2,2,3,3-tetramethylbutane, and the decanehaving five methyl groups.

Unless the octane mentioned before is present in admixture with theother products it cannot be handled satisfactorily because it is a solidat ordinary temperatures and pressures. There- While it is prefore. itis desirable to recover the product comprising the aforesaid trimethyland tetramethyl- 6 Table II Light source Mercury lamp.

butane and the pentamethylpentane in admlxfintncipal m length,Angstromsfl a ar, y k r i e 8.1 sens zer ercur ture with each other. Thesame holds true to Power input to lamp, products produced from otherfeed mixtures in 5 Power output of lamp. watts orde to obtain thebeneficial results theref o Feed g g For example, when propane andisopentane comg g temperature, 123 prise the feed mixture, the productwould include gg g gi g 35;;- 4 0 at least two trimethylpentanes,dimethylbutane and dimethylhexane, all of which have desirable 10Composition of product: Percep t qualities for use in a motor fuel and tis deslred gfijggggi'gglgiggfi that the product be used for such exceptfor 2,3-dimethylbutane removal of unreacted hydrocarbons. gggiggiggggggIf the rate of flow through the reactor is such 0 m 5 that appreciablequantities of the metal sensitlzer Olefins are carried out of thereactor in the product EXAMPLE II stream, then it may be desirable toinsert a device for recovering the metal sensitizer from A second runwas made employing a feed mixthe reactor efiluent. This may be in theform ture of isobutane and isopentane which was va- Of a condensermaintained at a low temperature p rized and passed through the reactormainin the case where mercury is the sensitizer tained at a reactiontemperature of 155 F. and metal, it may be a bed of a metal with which760 mm. pressure. The product was recovered mercury y be amalgamatedsuch, for examp and analyzed. Conditions for the second run as zinc orcopper. and an analysis of the product are presented in The inventionwill be further illustrated by T bl III, the following examples in whichfeed mixtures Table III were vaporized and heated to a reaction tem- L Might source ercur lamp. perature and pressure and then introduced intoPrincipal wave length Angstroms 2531 Y the inlet of an annular reactorof which a meryetal sensitgizerf t p r u ower inpu to amp, wa s 1 curylamp formed the inner cylinder and a Pyrex 39 Power Output of lamp watts2 9 glass acket formed the outer cylinder. The lamp Feed Approx.isobuhad an energy output of over of the emitted g 2+ radlation in theunreversed 2537 A. line. A small geaction temperature, F 155. amount ofliquid mercury was present in the gg igg g ggif g fi g 9 annulus tosupply mercury vapor to the hydro- 35 Com osition of roduct: P re tcarbons to act as a metal sensitizer for the re 2,2,aatetm fneth lentane 20 2,2,3,4-tetramethylpentane 15 action. During the react on theacket was 224* 2,3}; and 2y2y5 trimethylhexanes 15 heated externally tomaintain the reaction tem- 2,2,3,3-tetramethylbutane 1o perature.Pressures were substantially atmos 4o Q +pammns and 2O pheric. Duringthe time the run was conducted EXAMPLE 111 the feed was continuouslyintroduced at the inlet I th, 1 and product continuously withdrawn fromthe of s i gg 2%? i made W1 hdmlxtures outlet. The reactor efiluent waspassed through D p S u propane an 9 tane and n-butane and lsobutane. Thevarious condensers where the temperature was reduced t hase and a asbase which 4.) feed mixtures were vaporized and passed through 0 recoveratlqm p d g f d t d the reactor as has been described before. The weresepara ely recovered an ana yze 0 eproduct was recovered and analyzed.The retermme then composltlonsults of these runs and the conditionsunder EXAMPLE I whlch the runs were conducted are shown in 50 Table IV.In this run a feed mixture comprising pro- Table IV pane and n-butanewas vaporized and introduced Li M r into the reactor which wasmaintained at a tem- Pr mdfigitits rant?15555515523: 5%??? lamp'perature of F. and 760 mm. pressure. The E gi yresults of this run arepresented in Table II. power output of lamp, jj: :j 3

65 ropanc +357 Approx. 707 pro ane Feed isobutane o 30% j tg nllixwren'butalle lsoblltlme Reaction temperature, F 265 269 225 Reactionpressure, mm 760 762 762 Residence time, minutes 3. 5 3. 5 3. 7

Composition of product Component Percent Component Percent ComponentPercent 2,2,3-trimethylbutane. 22 2,3,3-trimethylpen- 352,2,3-trimethylpentane- 40 2, 2, 3, 3 tetramethyl 43 tane.3,4-dimethylhexane 15 butane. 2,3,4-trimethylpen- 202,2,3,3-tetramethylbutane 5 2,2,3,3,4- entamethyll7 tane.lzdimethylhexane 5 pentane. 2,3-dimethy1butane. l0 2,4-dimethylhcxane. 5Olefins 3 2,4-d1methylhexana} 9 2-methylhe tane; 4 Others 152,5-dimethylhexana 3-methylheptane 3-methylheptane 4 Olefins 114-methylheptane O thcrs 15 3,3,4,4-tetramethyl- 3 hexane. Olefins 10Others 9 3 EXAMPLE IV In this example 50430 mixtures of isobutane andisopentane were vaporized and passed through the reactor in the presenceof mercury at a temperature in the range between 120 and 140 F. atvarying feed rates. The products were collected and recovered andanalyzed. The results of these three runs are presented in Table Vwherein the operating data and the products composition are given.

Table V Light source G. E. 30-Watt mercury lamps.

Metal sensitizer Mercury.

Power output of lamp 2537 A., watts"... 7. 0.

Feed composition, mol. percent 50 isobutanc-50 isopentane.

Operating temperature, F 120-140.

Operating pressures, atmospheres 1, 0.

Feed rate, ccJmin 50 100 200 Conversion, percent of charge- 10. 5. 2 3.0

Mols. product per 4-l1rl period.. 0.027 0.028 O. 032

Product composition, mol. ,pcrcen 2,2,3,3-tetramethylpcntane.. 36 38 362,2,3,4-tctramethy1pentane l2. 5 l3. 5 13. 5 2,2,3,3-tetramethylbutanell. 5 9. 5 l1. 5 Trimethylliexanes 16 12 16 .Olefins 2 2 Ca+parafiinsand others 22 17 21 Bromine number of produc 4. 6 10.2 3. 5

In considering the runs represented in the several examples, it will beseen that the products vary in composition in accordance with the feedstock and that the product comprises mainly alkanes containingdime'thyl, trim'ethyl, tetramethyl groups substituted on the hydrogens.Furthermore, it will be seen that when the feed stock was propane andisobutane, the ratio of trimethylbutane to tetramethylbutane topentamethylpentane was approximately 2:4 :2. Examination of the productin each of the several examples indicates that the alkanes having from 2to 5 methyl groups substituted on the hydrogen atoms comprisedapproximately 60% by volume of the product. This in itself isadvantageous and. such a product will have a very high octane rating.One advantage from the present invention where tetramethylbutane isproduced is the fact that the tetramethylbutane is produced in admixturewith other branched hydrocarbons. The tetramethylbutane itself is asolid hydrocarbon which could not be handled ordinarily at ordinarytemperatures and pressures, but in a mixture as shown intheseveralproducts in the different examples with other hydrocarbons themixture is liquid and may be handled convention-- ally in fuel systems.The various products in themselves are unique in that they compriseessentially branched chain hydrocarbons to the substantial exclusion ofstraight chain hydrocarbons. Usually branched chain hydrocarbons areencountered in admixture with straight chain hydrocarbons and ordinarilythe branched chain hydrocarbons encountered in the prior .art areusually (11- and trimethyl alkanes substituted for hydrogens in themolecule. In the practice of the present invention a composition havingdimethyl, trimethyl, tetramethyl and even pentamethyl groups substitutedon the hydrogen atoms is obtained.

The nature and objects of the present invention having been completelydescribed and illustrated, what we wish to claim as new and useful andto secure by Letters Patent is:

1. A composition adapted for use as a motor fuel consisting of2,2,3-trimethylbutane, 223,3 tetramethylbutane, and 2.2.33}!pentamethyl' pentane in the approximate ratio of 2:4:2.

2. A composition adapted for use as a motor fuel consisting of a mixtureof trimethyl butane, tetramethyl butane, and pentamethyl pentane in theapproximate ratio of 2 :4 2.

HENRY G. SCHU'IZE. HARRY E. 'CIER.

References Cited in the file. of this patent UNITED STATES PATENTSNumber Name Date 2,491,983 Stanly et a1. June 11, 1946 2,406,667 ClarkeAug. 27,1946

FOREIGN PATENTS Number Country Date 465,459 Great Britain May 3, 1937578,552 Great Britain July 3, 1946 OTHER REFERENCES Aviation GasolineManufacture, Van Winkle, l-st Edit, McGraw-Hill Book Co. Inc. (1944),pp; 48 and 49.

1. A COMPOSITION ADAPTED FOR USE AS A MOTOR FUEL CONSISTING OF2,2,3-TRIMETHYLBUTANE, 2,2,3,3TETRAMETHYLBUTANE, AND 2,2,3,3,4 -PENTAMETHYLPENTANE INTHE APPROXIMATE RATIO OF 2:4:2.